Many known systems and methods have been developed in the construction industry for forming block retaining walls constructed for such purposes as hillside erosion control, substantial ground elevation changes in landscaping, and so on. In conventional art such retaining walls are constructed with blocks usually formed of heavy, high-density material, typically concrete. In some applications the blocks may be formed of solid stone material cut from a base stone material.
A disadvantage common to conventional retaining wall blocks is that, due to the dense properties of the concrete or stone materials forming the block, a single conventional retaining wall block is a heavy object in itself, often 70-100 pounds or more for a commonly sized block, difficult for many to lift and handle conveniently. Another inherent disadvantage in such heavy blocks is that, since transportation costs of such materials is directly affected by the weight of the transported materials from the store outlet or manufacturing site of the new blocks to a final destination, transportation is often cost prohibitive, particularly when the work site is located in a substantially distant geographic location from the source of the heavy blocks.
Construction of most larger retaining walls, such as those designed for retaining hillsides, particularly ones which may, at times, have substantial water drainage needs, usually involves a substantial amount of ground excavation and preparation along and behind the proposed line of the wall, and then layering successive layers of back fill and drain fill materials, and often other supplemental drainage systems which may be required for proper drainage behind the retaining wall, along with successive rows of retaining wall blocks. A drainage pipe, or “tile” as it is commonly known in the industry, is commonly utilized for displacement of water which has drained down to the lower row of the retaining wall blocks, channeling the water draining into the drainage tile from above, along the base of the retaining wall, usually behind the retaining wall base layer, and eventually outside of the retaining wall area. In some extreme water situations such as when retaining walls are located near and below bodies of water or above-ground or below-ground streams, or in geographic areas with high annual rainfall, where sudden and intense rainfall may greatly increase the water saturation of the ground being retained in a short period of time, additional vertical drainage columns are employed to add increased drainage capability to the system.
Retaining wall block designs known in the art have addressed the problem of the heavy weight of individual concrete or stone building blocks by the development in the industry of lighter-weight, modular building blocks, some also adapted for receiving heavy fill material into a hollow cavity within the block. A block of this sort is taught in U.S. Pat. No. 5,658,098, issued to inventor Mark A. Woolbright on Aug. 19, 1997. The surface area behind a finished retaining wall utilizing such waterproof blocks forms a waterproof wall, through which water draining down from the ground and fill materials, and possibly accumulating behind the retaining wall, cannot pass. In some instances extreme drainage flow may cause water to drain through the soil and drain fill and backfill materials at a rate that is greater than that of the drainage capacity of the entire system, which may cause an elevated water level behind the retaining wall, particularly if the undisturbed soil behind the wall has been previously saturated. In such instances when drainage capacity is suddenly exceeded, the sudden excess water flow has nowhere else to accumulate but upward from the bottom of the retaining wall as the fill material fields continue to fill with drainage overflow water.
What is clearly needed is a retaining wall block and drainage system having the advantages of the individual block being of a substantially lighter weight compared to conventional concrete or stone retaining wall blocks, thereby greatly increasing the cost-effectiveness of transportation and handling of the blocks between the source and the work site, while also providing means for increasing the drainage capability of the retaining wall drainage system. Such an improved system also incorporates both additional drainage capacity into the individual building blocks, and additional drainage capacity for water draining through the drain fill and back fill materials behind the wall that when combined, provide far greater drainage capacity than systems of conventional art as described above. The individual, lightweight, drainage-capable building blocks of the system of the invention are adapted for receiving heavy fill material at the work site, causing each individual block to be of sufficient weight for construction of a retaining wall according to industry standards.
The additional drainage capability provided in such a retaining wall block and drainage system provides advantages over conventional systems by enabling one to economically increase the overall drainage capacity of the system so as to accommodate much greater fluctuations in drainage flow due to heavy rains, and so forth, thereby also greatly reducing the amount of ground excavation and preparation necessary prior to wall construction, because much shallower drain fill and free-draining back fill fields are required behind the retaining wall due to the increased drainage capacity incorporated into the blocks of the retaining wall. Such a system therefore greatly increases the cost-effectiveness of overall construction of the retaining wall and draining system, and also that of transporting and handling the retaining wall blocks and back fill and drain fill materials, by reducing the needed amount of such materials, which are typically provided from outside of the work site, and also by eliminating the need for various separate horizontal or vertical drain conduit systems which are required in many applications utilizing conventional retaining wall blocks.
The wall block and drainage system of the present invention addresses all of the above-described problems in the prior art by providing means for increasing drainage capacity in a retaining wall drainage system utilizing for the first time new and novel drain-capable lightweight retaining wall blocks and drainage systems in embodiments which are described below in enabling detail.